I was revisiting some old car stuff I read about a few years ago, one of which was the Jensen 541/R. This had an Austin Limo engine (4 litre I6) and a quite an advanced (for the time) aero body made from glass fibre.
The interesting aspect is the grill block which could be opened and closed from the driver's seat via a lever - Closed = cd 0.36
Open = cd 0.39
These cd's aren't impressive now but this was the mid-1950s and in reality they were after MPH and not MPG although as standard this car had drum brakes so that wasn't such a clever idea... Later ones had a Chrysler V8, and disk brakes were an option which was pretty much always specified.